Pot Roast With Creamy Mushroom Sauce 1 (2 to 2 1/2 pound) boneless beef chuck roast 1 package dry onion soup mix 1 (10.75 ounce) can cream of mushroom soup Place roast into crockpot. Add soup mix. Top with soup. Cover. Cook on low for 6 to 8 hours, or until tender. Makes 6 to 8 servings.